The invention relates to technique practice implements for golf and is distinguished from exercise devices utilizing weight resistance for weight training, strength training or muscle conditioning.
The balance, felt heft and swinging weight of golf clubs have been measured and compared since around the year 1934 by measuring the moment (torque, or moment of force) of the golf club produced by the weight of the golf club acting at its center of gravity about an axis (or fulcrum) that is a predetermined distance from the butt end (proximal end) of the golf club. This moment has been known since about 1934 as the swinging weight, swingweight moment or simply the swingweight of the club. The most widely used predetermined distance from the butt of the club is 14 inches, but any other distance could be used; and 12 inches was proposed around the year 1948 but has not gained widespread favor in the golf club industry. The swingweight moment is directly expressed in terms like inch-grams. The golf club industry widely uses the “Lorythmic” swingweight scale to translate these inch-gram measurements into a letter and number scale like D2 which is equal to a 14 inch fulcrum swingweight moment of 6150 inch-grams. Each numerical step equals a 50 gram change in the swingweight moment. Swingweight moment is distinguished from moment of inertia which is very sensitive to the length of the golf club and is expressed in terms like gram-inches squared (gram-inches squared).
There are few, if any, neutrally weighted full length golf training aides, that is to say few that are not overly heavy and not substantially eccentrically off balanced relative to a conventional club. If a user desires a full size implement for practicing the golf swing that is weighted like and, when swung in the manner of a golf club, feels like a conventional golf club, the user is likely to choose a conventional golf club, with which the user can either practice his swing or hit balls on a driving range. Most golf swing training devices are consistently relatively heavy compared to a conventional golf club because their objective is muscle strengthening or muscle training. There is no shortened golf swing practice implement available that is weighted and balanced to feel like a conventional golf club and yet is substantially smaller than conventional golf clubs.
The prior art devices are typically either 1) heavier than a regular golf club for weight training, muscle training or muscle building, or 2) axially offset to exaggerate the release of the wrists in the swing. The devices disclosed by Matthews (U.S. Pat. No. 1,524,196) are both shortened and stated to be intended to feel like a regular golf club. However, the Matthews device is based on the calculation of the moment of the implement around the fixed point of the left shoulder of a golfer. This use of moment calculation of golf implements is inadequate to determine the “heft” or “swinging weight” of the implement which is believed to be a better determinant of the perceived feel of a club.
In 1934, Robert Adams patented the first “Apparatus for Measuring the Moments of Golf Clubs and the Like” (Adams, U.S. Pat. No. 1,953,916). Adams disclosed that the “heft” or “swinging weight” of a golf club could be measured and compared by determining the moment of the golf club “about a point a fixed distance from one end of the implement”; and then “found in actual practice that satisfactory results are realized if the fixed point is fourteen inches from the grip end.”
The Adams swingweight moment calculation is sensitive to changes in the center of gravity in the club itself. The Matthews' moment calculation is relatively insensitive to changes in the center of gravity in the club itself. The relatively long moment arms in the Matthews device reduce the importance of the balance, mass distribuition and feel of the practice implement itself. As a result, the Matthews moment calculation is not effective for determining how the exercise implement will “feel” when swung by a golfer. The resulting device “feels” like a regular golf club only if the wrists are not cocked in the backswing or uncocked in the downswing. The required stiff armed swing is not a golf swing. When swung like a regular golf club, with a regular golf swing, including the cocking of the wrists in the backswing, the uncocking of the wrists in the downswing, and the refolding of the wrists in the followthrough, the Matthews device would feel extremely light; its “heft” or “swinging weight” are not at all similar to a regular golf club. It offers too little of the swingweight moment of a regular length golf club around the center of motion of the hands and wrists. The center of gravity of the Matthews device is very near the end weight, and therefore not balanced like a regular golf club.
Neither the techniques used by Matthews and Adams are useful for very short clubs. For example, the Adams 14 inch fulcrum point swingweight scale cannot be used to measure the “heft” or “swinging weight” of very short practice implements when the total length of the device is shorter than the 14 inch fulcrum point or when the center of gravity of the device is at, near or inside the 14 inch fulcrum point.
Examination of other prior art devices does not reveal a training device that is both substantially shorter than conventional golf clubs and yet retains the feel of a conventional club when used in typical golf swings. What is needed is a training device that can be swung in the exact manner of golf motions while the user is in limited space and that at the same time provides the user with the same feel of a conventional golf club.